I had 16K last week MEL-SIN. I got the u/g and was very suprised to have been pre-allocated this seat. Surely it's sought after?! The flight wasn't full but wasn't empty by far.
On SeatGuru, 16K was said to have the staff seats infront but it turned out they were opposite 16A,B.
I was given 16A on my last op-up (LHR-HKG). I think because it's an emergency exit row it really isn't often pre-allocated and can remain open until the flight goes to airport control. I'm not too sure people actually care that much about those seats when flying in J.
Qantas used to have 2 upper deck configs - one that had 6x4 seating, the other had 5x4 + 1x2 seating. I think the crew seats used to be on the JK side on the 5x4/1x2 setup, but I'm not 100% sure. Either way, I believe that config is now gone on Qantas (anyone know for sure?)
My preference is downstairs, but then you have to contend with the 2/3/2 config. Works well when no-one is sitting in the middle of the block of 3 (ie the E seat), but otherwise can get a little cosy.